Wednesday, 4 December 2013

Measuring cognitive function in MS

Cognitive impairment: the elephant in the room. #MSBlog #MSResearch

"The study below tells us what we already know; MSers as a group are cognitively impaired and perform a cognitive task more slowly that healthy controls. The investigators make the case that their testing paradigm using reaction times and movement time in a visual search task was the best at discriminating between MSers and healthy subjects. Importantly their task did not show practice effects. Does this mean that this visual search task is a suitable method to assess cognitive impairment in MSers? I suspect not. The task needs to be clinically useful and have so called face validity; i.e. what does having slower reaction times and reduced ability to track visual stimuli mean to some with MS? Will they be worse at playing computer games? Will they make mistakes driving and be at greater risks of having accidents? Will the insurance industry penalize them for the latter? In addition, this test may be subject to variability based on whether or not the optic nerves have been involved by MS or not. I suspect MSers who have had previous optic neuritis will perform these tests poorly."

"These tests however will need to be validated in both cross-sectional and longitudinal studies and been shown  to correlate with other MS-related outcomes, including quality of life, before they will be used in clinical trials."

"I agree with the comment that we need to assess cognition as part of our routine clinical practice. Why? MSers with cognitive impairment are much more likely to be depressed and anxious and have fatigue. These can be treated. They are also at risk of being non-adherent to their medication which will impact adversely on their long-term outcomes. The cognitively impaired are also at greatest risk of becoming unemployed; detecting cognitive impairment and managing it may help keep them in work. Prevention is better that dealing with the consequences after the event. Finally, cognitive impairment is one of the hidden disabilities in MS and is associated with gray matter disease and brain atrophy; detecting it may also impact on clinical decision-making around risk-benefit decision making. I suspect that if you had mild cognitive impairment and were told your prognosis is poorer as a result of this hidden disability that you may be more inclined to accept the risk of higher efficacy DMTs. Do you agree? Maybe I am wrong."

Utz et al. Visual search as a tool for a quick and reliable assessment of cognitive functions in patients with multiple sclerosis. PLoS One. 2013;8(11):e81531.

BACKGROUND: Despite the high frequency of cognitive impairment in MS, its assessment has not gained entrance into clinical routine yet, due to lack of time-saving and suitable tests for MSers.

OBJECTIVE: The aim of the study was to compare the paradigm of visual search with neuropsychological standard tests, in order to identify the test that discriminates best between MSers and healthy individuals concerning cognitive functions, without being susceptible to practice effects.

METHODS: RRMSers (n = 38) and age-and gender-matched healthy individuals (n = 40) were tested with common neuropsychological tests and a computer-based visual search task, whereby a target stimulus has to be detected amongst distracting stimuli on a touch screen. Twenty-eight of the healthy individuals were re-tested in order to determine potential practice effects.

RESULTS: Mean reaction time reflecting visual attention and movement time indicating motor execution in the visual search task discriminated best between healthy individuals and MSers, without practice effects.

CONCLUSIONS: Visual search is a promising instrument for the assessment of cognitive functions and potentially cognitive changes in MSers thanks to its good discriminatory power and insusceptibility to practice effects.


  1. Firstly - sorry to be pedantic - but the opening statement isn't very well phrased: "The study below tells us what we already know; MSers are cognitively impaired and perform a cognitive task more slowly that healthy controls." MSers CAN BE cognivitely impaired and perform SOME cognitive tasks more slowly than healthy controls. In the tests in the above paper, the averages between MS and health differed (but not statistically significantly on all the tests) but the SDs were such that a number of those with MS scored better than the healthy controls. It is far from the case that all 38 MSers performed worse than the 40 controls. It is also noteworthy that the MSers were 8 years post-diagnosis, with a mean EDSS >3 and all had suffered a relapse in the past 12 months despite being on medication. I'm not trying to downplay cognitive impairment but these facts are important to bring perspective to the study. There is also some lack of clarity about the attribution of cognitive versus sensory/motor impairment for the most significant test - i.e. reaction time requiring physical touching of a point on a screen.

    Anyway, that aside - I think cognitive impairment is an interesting issue from the perspective of how to monitor it in an individual? Unless you have a pre-MS comparison, how do you know whether someone has been impaired if it is imperceptible to them? Being lower than 'healthy' mean doesn't mean they are impaired (c. 50% of people are lower than mean by definition), just as being higher than mean doesn't mean they haven't been impaired. Surely the only method that could work is to introduce serial testing whereby your scores on the relevant test are compared to aged-matched controls and if you are dropping down the centiles then there is something to worry about? I started to try and self-monitor using one of the online 'brain exercise' sites. One of the problems with this however is the practice effect - I was soon in the top 5% of all users but I don't know whether that is my cognitive prowess or just because I played a lot and so got good at the various exercises!

  2. definitely your cognitive prowess :-) (I don't know you, but this is clearly what the quality of your post points to, also!)


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